eHealth (Electronic Health) is an emerging medical service paradigm, which employs information processing and communications to enhance traditional medical services. Remote patient monitoring is an eHealth service, which is used to monitor biosignal data of patients in a stable condition. The biosignal data of a remote/mobile patient can be transferred and processed for diagnosis (e.g., cardiac disease patients by monitoring electrocardiogram (“ECG”) signal and blood pressure or diabetes patients by monitoring sugar level). Remote patient monitoring services can reduce the frequency of face-to-face meetings between patients and healthcare staff and also shorten the time required for treatment acceptance and better management of medication doses to patients. Wireless technologies have been used to improve the flexibility of remote patient monitoring to continuously monitor the status of patients even in presence of mobility. Related works on heterogeneous wireless networks and remote patient monitoring systems can be summarized as follows.
A. Heterogeneous Wireless Networks
Network selection is one of the major issues in heterogeneous wireless access [3]-[7]. The decision on network selection by a mobile user depends on the preference, application requirements, and network condition [3]. An intelligent network selection algorithm based on user utility was proposed in [4]. This user utility is a function of the transmission rate, and different applications can have different utility functions. The network selection algorithm in [5] took both network performance and network access cost into account. In [8], the problem of radio resource allocation for different service providers in a heterogeneous wireless environment was formulated as a noncooperative game and the solution was obtained in terms of allocated bandwidth in different service areas. In [9], a bandwidth aggregation scheme for real-time applications in heterogeneous wireless network was proposed. This scheme uses the earliest delivery path first (EDPF) scheduling to choose packets from different applications to be transmitted over multiple wireless interfaces so that the delay requirements are satisfied. In [10], to alleviate network congestion, a hierarchical radio resource management framework was designed for an integrated wireless local area network (“WLAN”) and cellular network.
Since mobile users need to be handed over between different types of networks (i.e., vertical handoff) mobility management is a significant issue in a heterogeneous wireless access environment [11]-[16]. The problem of admission control for vertical handoff in an integrated WLAN and code division multiple access (“CDMA”) cellular network was proposed in [11] where an optimization problem was formulated as a Markov decision process to minimize call blocking probability while satisfying the throughput and packet delay requirements. In [12], a performance analysis model was proposed for vertical handoff an integrated cellular network and WLAN.
B. eHealth Services Using Wireless Communications
For patients with cardiac diseases, ECG signal can be monitored and transmitted wirelessly to the healthcare center [17]-[19]. GSM (Global System for Mobile Communication) technology and wireless application protocol (WAP) were used in the airmed-cardio system [19] to provide out-of-hospital follow-up services to cardiac patients. Although a cellular network can provide wireless connectivity to highly-mobile patients, its capacity is limited. Besides cellular technology, new wireless technologies (e.g., IEEE 802.16-based (also known as Worldwide Interoperability for Microwave Access (“WiMAX”)) wireless metropolitan area network (“WMAN”) and IEEE 802.11/WiFi-based wireless local area network (“WLAN”)) are also adopted for remote patient monitoring services [20]-[24]. In [21], application of IEEE 802.16/WiMAX-based broadband wireless access technology for mobile telemedicine services (e.g., communication between an ambulance and hospital) was discussed. Also, in [21], a bandwidth allocation and admission control scheme was designed specifically for telemedicine services over a WiMAX network. WiFi technology, which provides large transmission capacity in a small coverage area, can be used locally in a hospital, clinic, and home environment for patient monitoring, clinical alarm notification, workstation on wheels [22], ECG monitoring [23], and telehomecare. Also, WiFi networks are suitable to provide best-effort data communication services for commercial and support applications (e.g., guest access and patient billing [22]).
The concept of using heterogeneous wireless access networks for remote monitoring service was introduced in [25], where a general system model was presented for different eHealth services (e.g., intra-hospital, pre-hospital, tele-homecare, and follow-up services) based on heterogeneous wireless access. Also, a bandwidth allocation and admission control method was developed based on resource sharing using game theory. However, optimization of capacity reservation in the radio access network and issues related to queue management and transmission scheduling in a patient-attached device were not considered.
However, since the traditional remote patient monitoring systems rely on a single wireless technology, they are unable to guarantee that the patients will be “always-connected” with the eHealth service provider (e.g., healthcare center) when the patient roams through different locations.
It is, therefore, desirable to provide a patient monitoring system that implements wireless technologies to enable continuous and ubiquitous patient monitoring wherever and whenever the patient needs.